Electro-optic frequency shifters, or modulators, have been built with almost 100 percent efficiency. Conversions over 50 percent require the interaction of a circularly polarized high power microwave beam traveling synchronously with a circularly polarized laser beam in an electro-optic crystal. We describe the inhomogeneous quarter-wave transformer structures made for a CO2 laser beam modulator with a conversion efficiency in excess of 80 percent. Conventional impedance matching synthesis was adapted to include the requirements for maintaining circular polarization and handling high power. Measured results are presented.
Neville W. Harris,
D. M. Wong,
"Inhomogeneous quarter-wave transformers for a waveguide electro-optic modulator", Proc. SPIE 1416, Laser Radar VI, (1 August 1991); doi: 10.1117/12.43714; https://doi.org/10.1117/12.43714